Users often share links to content items (e.g., pictures, videos, songs, articles, etc.) provided by a networked content provider with others via online social networking communities, messaging applications, blogs, and other networked sources. Knowing the source (referred to herein as the “referral source”) from which a user was directed to a content provider's source based on selection of an inbound hyperlink, located at the source, to content at the content provider's source, can be useful to the content provider. For instance, by knowing the referral source, the content provider may recommend other content items to the user that are popular amongst users of the referral source. Although some browsers have the ability to detect a referral website, mobile applications and operating systems do not employ this functionality.